Plenty of business companies use free Asterisk software and place it on their server, thus creating a cut-rate IP-PBX. They use manuals provided on setting up the extensions, and occasionally there are lots of discrepancies. Finding out how to install a dial plan or call flow, the set of regulations detailing how the switch deals with inbound and outbound calls is very difficult.
Orpheum offers its iVoice (SIP trunking) and hPBX (Hosted/Virtual PBX) services exclusively to businesses in the USA and Canada. Both services start at $25 per month.